A fuel injection system for an automotive engine, in which electromagnetic fuel injectors deliver fuel from a fuel rail to the engine inlet manifold adjacent the engine combustion chamber inlet ports, ordinarily includes a fuel pressure regulator to control the pressure of the fuel in the rail. In such a system, the pressure in the fuel rail is usually controlled to maintain a constant pressure difference across the injector--from the pressure in the fuel rail to the pressure in the manifold. The fuel pressure regulator accordingly is connected to the inlet manifold to sense the manifold pressure, and to the fuel rail to sense the fuel pressure in the rail and to discharge excess fuel from the rail so the fuel pressure in the rail varies with the manifold pressure and is maintained at the desired difference above the manifold pressure.